Modified Atmosphere Packaging (MAP) of Food

Modified Atmosphere
Packaging
Ayesha Siddiqa
Ph.D. Scholar

MAP
 “Controlled atmosphere” and “modified atmosphere”
are terms implying the addition or removal of gases
from;
 Storage rooms
 Transportation containers or
 Packages
In order to manipulate the levels of gases such as oxygen,
carbon dioxide, nitrogen, ethylene etc., and achieve an
atmospheric composition different to that of normal air
around the food

History:
 Controlled/modified atmosphere is a relatively old
process
 Based on ancient writings, certain forms of modified
atmosphere storage were used in China, Greece, and
other early civilizations.
 According to some such reports, fruits were sealed in
clay containers together with fresh leaves and grass
 The high respiration rates of leaves and grass,
combined with that of the fruit, quickly modified the
atmosphere in the container, creating an environment
high in carbon dioxide and low in oxygen, which helped
retard fruit ripening
MAP

MAPofMeat
 However, it was not until 1820 that the effect of
atmosphere on fruit ripening was studied (Floros,
1990)
 About 100 years later, the effect of carbon dioxide and
oxygen concentration on the germination and growth of
fruit-rotting fungi at various temperatures was
investigated (Brown, 1922)
 Similarly, in the 1930s a number of research studies
were published regarding the effect of carbon dioxide
and storage temperature on the inhibition of microbial
growth on meat surfaces and the resulting extended
product shelf life

 The first significant trials of retail size modified
atmosphere packaging took place in the late 1950s,
with vacuum-packed meat, fish and coffee
 The interest in gas preservation techniques increased
dramatically in the 1970s and 1980s, and commercial
applications of MAP have steadily increased since
then.
 MAP seemed to be the ideal method of preservation of
many foods, because it could extend the shelf life of the
product significantly, without affecting its “fresh” or
fresh-like characteristics
 Nowadays, MAP has become an integral part of the
food industry, particularly the fresh produce industry,
and it is more important than freezing and canning
combined.

Principlesof
MAP
 The objectives of MAP are;
 To extend the shelf life of food products
 To prevent (or at least retard) any undesirable changes
in the wholesomeness, safety, sensory characteristics,
and nutritive value of foods
 MAP achieves the above objectives based on three
principles:
1. It reduces undesirable physiological,
chemical/biochemical and physical changes in foods
2. It controls microbial growth
3. Just like any other packaging technique, it prevents
product contamination.

GASESusedin
MAP
 The three main gases used in MAP are nitrogen (N2),
oxygen (O2), and carbon dioxide (CO2)
 At sea level, the approximate composition of
atmospheric air is 78.1% N2, 20.9% O2, and 0.03% CO2
 The role and the importance of each gas in MAP are
related to its properties
 Nitrogen is an inert and tasteless gas, without any
antimicrobial activity
 It is not very soluble in water, and it is primarily used
to displace oxygen and prevent package collapse.

Whytoremove
oxygen?
 Oxygen inhibits the growth of anaerobic micro-
organisms, but promotes the growth of aerobic
microbes
 Additionally, oxygen is responsible for several
undesirable reactions in foods, including;
Oxidation and rancidity of fats and oils
 Rapid ripening and senescence of fruits and vegetables
Staling of bakery products
Color changes
Spoilage due to microbial growth
 Due to oxygen’s negative effects on the preservation of
the food quality, it is generally avoided in the MAP of
many products

Oxygen
CarbondiOxide
 However, its presence in small quantities is at times necessary for
some products.
 For example, a minimum oxygen concentration is required by many
fruits and vegetables in order to sustain their basic process of aerobic
respiration.
 In other cases, such as red meats, high oxygen concentration is used to
initiate “bloom” and preserve the bright red color of fresh meats.
 Carbon dioxide is soluble in both water and lipids, and its solubility
increases with decreasing temperatures
 The dissolution of CO2 in the product can result in package collapse
 Carbon dioxide has a bacteriostatic effect, and it slows down the
respiration of many products.
All three gases are common and readily available, safe, economical, and
are not considered to be chemical additives. However, the optimum level
of each gas for each food product must be determined and used in order to
maximize the positive and minimize the negative effects

Othergases
 In some cases, additional gases are used in
combination with the above mentioned gases
 Carbon monoxide (CO) is sometimes added to inhibit
microbial growth
 However, CO is toxic to humans, and its application is
limited.
 Sulfur dioxide (SO2) may be used to prevent oxidative
browning and to control the growth of bacteria and
molds
 Ethanol has also been used to enhance the firmness of
tomatoes, improve flavor, and reduce fungal activity,
and argon has been used to reduce microbial growth

MAP
Techniques
 The atmosphere inside a package can be modified by
either passive or active means
 In the first case, the rate of change and the final gas
composition in the package depend largely on both the
packaged product and the permeability of the packaging
material.
 It is well known that most foods come from living entities
and continue to live after harvesting
 Fruits and vegetables, for example, consume the oxygen of
the surrounding environment and release carbon dioxide
via the respiration process
 Similarly, the natural microflora of many products also
consume oxygen
 Besides the biochemical and physiological processes that
utilize the available gases, oxidative reactions also take
place during the storage period of foods, resulting in a
reduced oxygen concentration over time

 If the above phenomena occur in a sealed package,
impermeable or permeable to gases, the gas
composition inside the package will change.
 If the container is impermeable to gases (e.g. glass jars,
rigid metal cans, barrier plastic films), the rate of gas
production and/or consumption will dictate the gas
composition at any time
 However, if the container is permeable to gases (e.g.
flexible non-barrier plastic package), the gas exchange
with the environment will also take place through the
package
 As a result, the gas composition inside the package will
be further modified and the final gas composition will
be different in the two containers

 The main disadvantage of the passive atmosphere
modification method is that the desired atmosphere
is achieved very slowly (Figure)
 This can sometimes result in uncontrolled levels of
oxygen, carbon dioxide or ethylene, with a
detrimental effect on the quality of the product
 Active modification of the atmosphere can provide a
solution to this problem
 This is usually accomplished by first creating a
vacuum and then incorporating the desired gas
mixture in the package
 Compared to the passive method, active atmosphere
modification is practically instantaneous and takes
place at the beginning of storage
 The atmosphere should then remain practically
unchanged, provided that the proper barrier
material is used and there is no leakage through
pinholes or poor seals

Active
Atmosphere
Packaging
 The process of applying a vacuum can be considered a
method of active atmosphere modification
 It is commonly used in packaging techniques such as
canning, or bottling in glass containers
 The main purpose of such vacuum application is to
reduce the residual oxygen in the headspace of a
package, which eventually retards oxidative chemical
reactions and aerobic microbial growth
 When a vacuum is used with flexible packages, the
packaging material collapses around the product and
practically eliminates the existence of the headspace

Hypobaric
storage
 A vacuum is also often applied to storage rooms and
transportation containers, a technique called hypobaric
or low-pressure storage
 In this method, a slight vacuum is maintained in the
storage room or container, which reduces the partial
pressure of oxygen and continuously removes
undesirable gases such as ethylene
 As a consequence, oxidative and physiological reactions
are retarded

Active
Packaging
 Finally, relatively recent technological innovations
allow for in-package control of a specific gas (oxygen,
carbon dioxide or ethylene)
 Such “active” packaging systems are designed to
remove or add certain gases selectively
 This is usually achieved by using a substance that can
bind (scavenger) or release (emitter) certain molecules
as a result of chemical or enzymatic reactions
 The “active” substance can be placed in the package
(e.g. in a sachet), or in more sophisticated systems it
can be incorporated into the packaging material itself
The method is referred to as active packaging

 An example of this technique is the addition of small
sachets in cans of coffee
 The sachets contain a mixture of iron oxide and
calcium hydroxide that binds oxygen and enables the
control of the package environment without gas-
flushing or the application of a vacuum

Advantages
 MAP offers many advantages to consumers and food
producers
 To the consumer, it offers convenient, high-quality food
products with an extended shelf life
 It also reduces and sometimes eliminates the need for
chemical preservatives, leading to more “natural” and
“healthy” products
 At the same time, producers also enjoy the benefits of
increased shelf life
 By using MAP many products can be packaged centrally,
and their distribution cost is reduced because fewer
deliveries over longer distances become possible
 Moreover, because of the extended shelf life, MAP allows
transportation of foods to remote destinations and
increases product market

 MAP offers many advantages to consumers and food
producers
 To the consumer, it offers convenient, high-quality food
products with an extended shelf life
 It also reduces and sometimes eliminates the need for
chemical preservatives, leading to more “natural” and
“healthy” products
 At the same time, producers also enjoy the benefits of
increased shelf life
 By using MAP many products can be packaged centrally,
and their distribution cost is reduced because fewer
deliveries over longer distances become possible
 Moreover, because of the extended shelf life, MAP allows
transportation of foods to remote destinations and
increases product market

Disadvantages
 MAP also has several disadvantages
 Usually, each MAP product needs a different gas
formulation
 This requires the use of specialized and expensive
equipment
 At the same time, production staff must receive special
training. For most products, storage
 Temperature control is required and product safety must
be established
 Furthermore, MAP causes larger package volumes, which
leads to increased transportation and retail display space
needs
 All the above add a noticeable cost, which must be paid by
the consumers
 Finally, another disadvantage of MAP is that it loses all
its benefits once the consumer opens the package.

Modified Atmosphere Packaging (MAP) of Food

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